Wednesday, January 14, 2015

WHO/FAO/OIE Announce A New H5 Clade (2.3.4.4)

While working on a completely different blog topic this morning (H5N5 receptor binding . . .stay tuned) I ran into the following statement by the WHO/OIE/FAO on a new H5 clade 2.3.4.4 designation, into which many of the recent H5 viruses reported in Europe, Asia, and North America will now apparently fall.

12 January 2015

Recent detections of highly pathogenic avian influenza A(H5N8) in East Asia and Europe, A(H5N8) and A(H5N2) in North America, and A(H5N6) in East and Southeast Asia, have prompted the WHO/OIE/FAO H5 Evolution Working Group to review and update the H5 haemagglutinin (HA) clade nomenclature (1-4), which was last revised based on sequence data available prior to December 2012 (4).

Although a detailed report describing the update of the existing nomenclature is in preparation, considering the high likelihood that these viruses will continue to be detected and reported, timely communication of the new clade designation is warranted. The phylogenetic analysis of H5 HA sequences from these viruses revealed extensive divergence and indicated the need to update the clade nomenclature for H5N1, H5N2, H5N5, H5N6, and H5N8 subtype viruses clustering in this HA group.

After careful analysis of all available H5 sequence data, this group of HA gene segments has been designated as clade 2.3.4.4 and use of this unified classification is recommended. The virology, animal and public health communities are encouraged to adopt this clade designation for these H5 HAs and discontinue use of the provisional clade 2.3.4.6 designation, which was assigned tentatively during the WHO Vaccine Virus Consultation in September 2014 in reviewing and selecting candidate vaccine viruses of this emerging group of viruses (5).

Clades are branches on the family tree, and the H5 family tree has grown spectacularly over the past 18 years. Although the chart below will now have to be revised due to this new clade designation, it gives you some idea of the genetic diversity of H5N1 around the globe.

With HPAI H5 promiscuously sharing genes with other influenza viruses, these H5 clades are no longer just found in H5N1, but are also found in H5N2, H5N3, H5N5, H5N6, and H5N8 as well.